The invention relates to a device for treating at least the bottom of a disc-shaped object. Disc-shaped objects include semiconductor substrates such as silicon wafers, gallium arsenide wafers, but also glass discs, quartz discs, metal discs, flat-panel displays as well as so called hard disks and compact disks (CDs).
Treatment of surfaces of the disc-shaped object can for example be for the purpose of etching, cleaning, application of layers (e.g. electroplating) or for developing photosensitive resist.
During such treatment, liquids (either identical or different) can be applied to one or both surfaces of the disc-shaped object. If the same liquid is applied to both surfaces, said liquid can be collected and returned. The use of two different liquids may be necessary if e.g. one surface (the front) is etched and the other surface (the reverse) is to be protected at the same time against etching.
U.S. Pat. No. 5,375,291 A describes a device for simultaneous treatment, with liquid, of both surfaces of a disc-like object. The device comprises a rotatable carrier for holding the disc-shaped object and comprises means for applying a liquid to both sides of the object. The carrier is driven via a rotatable hollow shaft. Within the rotatable hollow shaft there is a stationary hollow shaft. The treatment liquid is supplied through the stationary hollow shaft. The rotating hollow shaft forms the shaft of a so-called hollow-shaft motor.
There is a disadvantage in that liquids and solids particles, for example caused by bearing abrasion, can enter through an open gap between the stationary and the rotating hollow shaft. This is associated with the danger of the disc-shaped object being contaminated.
According to JP 09-314023 A this problem is solved in that a cover is arranged above the gap. In addition, a labyrinth seal is arranged between the rotating part of the carrier and the cover. However, even then the results of the process are unsatisfactory. If previously several wafers were treated, the surface of the disc-shaped object which faces the carrier becomes contaminated. Investigations have shown that droplets of liquid also deposit on the cover.
It is thus the object of the invention to provide a device of the type mentioned, with which contaminations of the disc-shaped object can be reduced or prevented. This applies both to contaminations resulting from particles from the mechanical arrangement and from contaminations as a result of deposited droplets of liquid.
The invention is based on the following idea:
If a stationary device (cover) is arranged directly below the disc-shaped object to be treated (hereinafter referred to as a wafer), for example around the supply line for a treatment medium, turbulences occur in the space below the wafer, said turbulence causing the problems mentioned. The invention therefore uses a different approach: no further components are arranged between the rotatable carrier used for accommodating the wafer, and the wafer itself. The invention takes into account that by necessity there is a gap between the (stationary) supply line for the treatment medium and the rotating carrier, with droplets of liquid or dust particles being able to enter through said gap. According to the invention, elimination of said droplets of liquid or dust particles is effected by a stationary component of the device, hereinafter called the xe2x80x9ccoverxe2x80x9d, arranged below the carrier. Between the above-mentioned gap in the region of the upper face of the carrier in its extension, a further gap between the bottom of the carrier and the top of the static cover has been provided, by way of which gap said droplets of liquid and solids particles are able to be led away. Due to the rotational movement of the carrier in relation to the static cover, in this region of the gap, turbulence and centrifugal forces act on the foreign particles which in this way can safely be led away to the outside (radially in relation to the above-mentioned supply line for the treatment medium).
In its most general embodiment, the invention thus relates to a device for treating at least one bottom of a disc-shaped object with the following features:
A rotatable carrier with an upper face from which, perpendicular to the upper face of the carrier, at least two devices protrude for positioning the discshaped object;
At least one line for supplying a treatment medium against the bottom of the disc-shaped object, said line being arranged so as to be stationary and so as to penetrate the carrier at its centre;
A cover, arranged so as to be stationary, forming an annular gap and spaced apart from at least one section of a lower face of the carrier; with said cover being penetrated without leaving any clearance, by the line, of which there is at least one.
According to the first partial feature, the rotating carrier comprises at least two devices for positioning the wafer. Usually, at least three such devices are provided, for example at an angular spacing of 120 degrees in relation to each other. Such devices, also known as pins, can be arranged so as to be radially adjustable in order to guide/grip the wafer. The following description of the figures provides further information.
According to the second partial features, at least one treatment line leads through the device, preferably in the central longitudinal axis or parallel to said central longitudinal axis of the device, and thus perpendicular to the alignment of the wafer. Liquids or gasses for treating the wafer can be led through this line (these lines). Furthermore, one line can also be an optical waveguide which is for example used to detect light reflected from the bottom of the wafer. This waveguide can thus indicate a state in which treatment is completed. The waveguide can also indicate whether or not a wafer is in place at all.
The third partial features provides for a stationary cover, arranged below the carrier and spaced apart from said carrier. This stationary cover is free from play (seamlessly) connected to the stationary line(s). This results in a continuous channel (gap) extending from the upper face of the carrier, adjacent to the line(s), to the gap between the cover and the carrier. As explained below, this gap should be continued radially and open to the outside.
The purpose and function of the gap have already been described above.
According to one embodiment, the cover, adjacent to the line of which there is at least one, can comprise an inner part extending parallel to the upper face of the carrier, and an outer part, towards the margin, said outer part being inclined downwardly with respect to the upper face of the carrier. In this way, the radial removal of foreign particles or particles of liquid is facilitated.
So as to achieve a constant gap height, the lower face of the carrier can be constructed so as to correspond with the cover. According to a further embodiment the carrier protrudes from the cover on the outside and thus radially with respect to the line(s). This embodiment is also shown and explained in the following description of the figures.
The cover can be seated so as to be stationary, on a tubular body which accommodates the at least one line. The tubular body can be routed in the direction away from the upper face of the carrier through the device and onward to a stationary bottom.
According to a further embodiment, an annular disc follows the lower face of the carrier, towards the margin, said annular disc encompassing the line(s) at a distance; along its outer part said annular disc being connectable to the carrier and moreover may extend at a distance to the cover.
As an extension of the annular gap, between the carrier and the annular disc, at least one gap, essentially extending radially to the at least line can be arranged. Said gap creates the extension of the above-mentioned gap regions between the carrier and the line or between the carrier and the cover to the outside, so as to remove droplets of liquid or solids particles which as a result of rotary movement of the carrier or of the disc relative to the cover, under the influence of centrifugal forces, are removed to the outside.
Preferably a multitude of gap sections are provided between the outer section of the carrier and the outer section of the annular disc, with the individual sections again optionally being arranged around the circumference, at even angular spacing relative to each other.
On the inside, the annular disc which is arranged to rotate together with the carrier, can be guided on a rotary bearing which rests against the above-mentioned tubular body which carries the cover.
Furthermore, the annular disc may comprise a tubular extension, in particular on its inner part, said extension being aligned parallel to the line of which there is at least one, in the direction away from the lower face of the carrier and thus parallel to and spaced apart from the tubular body. The spacing between the tubular extension and the tubular body is important because a rotary component (the tubular extension) has to be positioned against a stationary component (tubular body). The tubular extension at the disc can be coupled to a rotary drive. For example the drive can be a motor whose rotor is connected to the tubular extension and whose stator rests against the tubular extension by way of at least one rotary bearing.
Apart from the treatment of the bottom of a wafer, as described, the device may comprise a further supply arrangement for a treatment medium above the wafer, so as to treat the top of the wafer too. In both cases the respective lines are stationary, without any interference from rotating components. Despite there are no problems when sealing the rotating components in relation to the stationary components.
Further features of the invention are provided in the features of the subclaims as well as in the other application documents.